Stabilizing means for high pressure hy-



Dec. 23, 1958 R. F. HODGSON 24530 STABILIZING MEANS FOR HIGH PRESSURE HYDRAULIC VALVES OF THE PLUNGER TYPE Original Filed Sept. 10, 1956 2 9 O 9 wwg fi 2 B 3 LI'I/ r 4 o o 5 o o G G. .l \1\:O O .1 F 0 F a 5 6 7 92 2 A l l 13 l4. 5 a d 111i: A; .2 2 vvvvwvbvv O m a 2 3 B 3 f 20 0 1| 6 d \5 lb 0 Z 4 J ZW 3 9 l m mm g d O H F n 8 b O 3 R 5% 1 O 3 w l T e i F United States Patent STABILIZING MEANS FOR HIGH PRESSURE HY- DRAULIC VALVES OF THE PLUNGER TYPE Mich., assignor to The Brake Company, a corporation of New Robert F. Hodgson, Kalamazoo,

New York Air Jersey 7 Claims. (Cl. 137-622) Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

This invention relates to plunger valves, and more particularly, to an improvement therein for substantially relieving the unbalanced axial force resulting from the dynamic reaction of the fluid flowing therethrough.

Most of the plunger valves in use today, employ a movable plunger having one or more longitudinally spaced lands of relatively large diameter separated by neckeddown regions of relatively small diameter. The annular shoulders presented by these lands, between the outer surface and the surface of the reduced portion, normally comprise a small radius fillet at the neck and a flat face perpendicular to the axis of the plunger. This flat face meets the outer surface of the land at an angle of 90, thus forming a sharp control edge.

These plungers are used in conjunction with seat lands of similar shape defined in the bore of the valve housing by annular grooves. These encircle the cylindrical bore which receives the plunger. The control edge of the plunger land and the square edge of the associated fixed scat land, constitute an adjustable annular orifice, the width of which determines the degree of communication between flow chambers disposed adjacent each side of the fixed land.

Fluid which flows between the chambers through the adjustable orifice and across the fixed land, experiences a change in momentum regardless of the direction in which it flows, and this change in momentum is accompanied by a corresponding dynamic reaction upon the plunger. Since it is well known today that the direction of flow through these adjustable orifices is not parallel with the end face of the land but rather is at an angle to such face, it becomes obvious that this reactive force will have components in both the radial and axial direc tion's. If the port is a complete annulus, the radial components will balance out but the axial components will remain unbalanced.

Up to this time, various attempts have been made to compensate these axial forces or to eliminate them entirely, but since the problem has evaded mathematical statement, the solutions have not been altogether satisfactory. It has been determined however, that such quantities as velocity, pressure drop and rate of flow, cause the development of these forces. Influenced by these findings, the prior art discloses the use of throttling grooves, notches and chamfers placed on the edge of the plunger land, in an effort to reduce the effect of one or more of these variables. These 'expedients have met with varying degrees of success, but the problem still ersists.

The object-of this invention is to provide an improved plunger valve in which the axial [forces are substantially balanced] component of the dynamic reaction force at any position of the plunger is less than the force exerted by the plunger-biasing spring at the same position. Briefly, the invention involves the provision of a separate ice flow path through the plunger itself which is in parallel flow relation with, but completely distinct from, the normal path across the edge of the plunger land. In its preferred form, this second path comprises an undercut in the face of the plunger land beneath the control edge and a plurality of small-diameter radially-extending pas: sages communicating between this undercut and the peripheral surface of the plunger land at points axially displaced from the control edge. The effect of this path is twofold: First, it by-passes a portion of the flow and consequently reduces the momentum of the fluid flowing through the adjustable orifice, thereby decreasing the reactive force on the plunger and, of course, the axial component thereof. Second, the fluid which is diverted is conveyed to the downstream chamber along a path normal to the plunger axis and consequently produces a substantially radial reactive force on the plunger. in the case of a symmetrical series of radial passages, this latter force is completely balanced, thereby eliminating possible binding of the plunger in the bore.

in actual comparison tests of this arrangement with the grooves, notches and chamfers of the prior art, it was shown that the present structure affords vastly superior performance.

The invention will now be described as embodied in a known type of open-center plunger valve, for controlling a double-acting motor, said valve having a normal or centered position in which it hydraulically locks the motor and unloads the system by connecting the main supply and exhaust flow connections, two motor-energizing circuit-loading positions in which, respectively, it charges a selected working space exhausting the other working space, in which it connects both working spaces to exhaust.

The invention will be shown embodied in the two con.- trol edges of the open center, because here the heaviest flows and greatest changes of pressure occur.

In the drawings:

Fig. 1 is an elevation. view of the valve including, in schematic form, the actuator and centering spring.

Fig. 2 [l] is an axial section of the [a simplified] valve showing the piunger in its normal position.

Fig. 3 [2] is a fragmentary view part in section, showing on an enlarged scale the control edges of the plunger which perform the unloading and loading functions, and embody the significant feature of the invention.

Fig. 4 E3] is a fragmentary view showing a control edge of the valve as it engages the seat land.

Referring to the drawing, the invention is shown incorporated in a plunger valve which comprises a housing 11 having a through cylindrical bore 12 which snugly but slidably receives the plunger element 13. The housing 11 contains annular chambers 14, 15, 16, 17, 18, 19 and 21 each of which encircles the through bore 12 and which are separated by seat lands as shown. The chambers 16 and 19 communicate with inlet port 22 via passages 23 and 24 respectively; the passage 23 having conventional check valve 25 disposed therein. The chambers 14, 13 and 21 communicate with the common return passage 26 which connects them to the return connection 27. Chambers 15 and 17 are connected to motor ports 28 and 29 for controlling a reversible fluid motor (not shown) as hereinafter described.

The plunger element 13 comprises lands 31, 32, 33 and 34 separated by reduced diameter ,or necked-down portions, as shown. At its upper end, the plunger is formed with a suitable fork ,35 for connection to actuator" 30 [actuating means (not shown')'] and at its lower .end carries a shoulder 36 for limiting the upward travel of the plunger. The downward travel of the plunger is of the motor while and a float position of the motor part in elevationand y any suitable attaching means (not shown) and which abuts the end of the plunger in the lowermost position.

The edges 38 and 39 of the lands 33 and 34 respectivcly, have been modified in accordance with the preferred form of this invention. which is an modified in exactly the In operation, the ports 28 and 29 are connected to opposite sides of a reversible fluid motor and the return port 27 is connected to a Fluid under part of the fluid entering chamber 21 crosses flows into recess the valve poor control characteristics.

In the v 42 to be completely enclosed within the fixed land 20.

In this uppermost position of the plunger, the flow to chamber 21 is completely shut-ofi and the total volume of fluid entering inlet port 22 is conveyed to motor port ?9 by check valve 25, passage 23, annular chamber 16,

move between plunger lands 3] and 32, annular chamer 14Qana common return passage 26 [chambers 16 receive the total volume of n ering inlet port 22.] Since one side of the fluid motor is now pressurized and the other is connected to the return line, the motor will move in the first of its two directions.

If the plunger is permit chambers 15 and 17 and motor port 29 fluid t now displaced downward so as to and 16 to communicate across the adjustable orifice such as is de- 20 and [34] 33 balanced the spring [actuating mechaust prior to complete interruption of the flow to chamber 21. Incorporation of the present invention in the land 33 relieves the problem in the same he significant diflerence in operation between these two Installations is the direcof the forces.

If the plunger is now moved to its lowermost position, into abutment with casing 37, the land 32 will move com pletely within the chamber 17, thus causing [interconnecting] chambers 15 and 17 to be interconnected by the groove between plunger lands 31 and 32, and chamports 28 and 29]. land 33 will continue to block [the return] flow between [to] chambers 19 and 21 but since the upper edge of this land I 9, the groove between plunger lands 32 and 33, chamber 18, and return passage 26, [chambers 18 and 19,] the pump will be unloaded. This position of the plunger is commonly called the float position, as the fluid motor can be manually moved in either direction without resistance from the pressure fluid.

Since, in the normal applications of the valve, the

the land 20 is large. For this reason, the invention has been applied to the land edges 38 and 39 which control this port. It should be understood, however, that the balances are not as great.

In summary, it is important to note that the passages 42 need not extend through the is, to a large extent,

the scope of the inventive concept should not be limited in any respect except in accordance with the following claims.

What is claimed is: g

[1. In a valve, the combination of a housing having a cylindrical bore and two axially spaced flow chambers intersecting said bore; a cylindrical seat land encircling said bore and interposed between said two flow chambers; a plunger slidably mounted in said bore and having a peripheral control edge which coacts with said seat land to form a variable area flow path between said chambers; means for moving said plunger between a first position in which the variable flow path is completely closed and a second position in which said flow path is opened a predetermined maximum amount; and a separate flow path formed in said plunger for providing parallel flow between chambers, said separate path comprising a first portion extending axially inward from the end face of the plunger beneath said control edge and a second portion extending in a direction normal to the axis of the plunger from said first portion through the surface of the plunger at a point axially remote from the control edge] [2. The combination defined in claim 1 in which the second portion of said separate flow path comprises a circumferential series of radially-extending passages] [3. The combination defined in claim 1 in which the second portion of said separate flow path comprises a circumferential series of radially-extending passages'arranged such that they are closed by said cylindrival valve land during a portion of the limited movement of said plunger] [4. The combination defined in claim 1 in which the first portion of said separate flow path comprises a conical recess and the second portion of said path comprises a circumferential series of radially-extending passages] [5. The combination defined in claim 2 in which the axial dimension of said radial passages is small in relation to the length of said passages] [6. In a valve, the combination of a housing having a bore for a plunger and two chambers communicating with said bore and located on opposite sides of a plungerfitting land, there being means supplying pressure liquid to one of said chambers and means venting the other chamber; a plunger movable axially in and fitting said bore and said land, said plunger having a groove serving to bridge said land when the plunger is in its mid position and thus connect the chambers, said groove affording opposed control edges on the plunger which may selectively overtravel control edges on said land to isolate said chambers when the plunger is displaced from said mid position, there being flow passages which lead from said groove through said plunger to the periphery of the plunger, said passages each including a terminal portion which lies in a plane normal to the axis of the plunger, the terminal portions being so located as to be closed by said land only when the plunger is moved from mid position a distance greater than that which causes a control edge on the plunger to overtravel a control edge on said land] [7. In a valve, a housing having a cylindrical bore, two flow chambers communicating with said bore, and a seat land encircling said bore and separating said chambers; a plunger movable in said bore and having peripheral ontrol edges which coact with said land to define variable area flow paths, means for moving said plunger between a first and second position in each of which the variable flow path i completely closed, and at least one position between the first and second positions in which said flow path is open; and separate flow passages formed in said plunger for affording flows between said chambers, said separate flow passages each comprising a first portion extending inward beneath one of said control edges and a second portion extending in a direction normal to the 6 said first portion through the point spaced from the control axis of the plunger from surface of the plunger at a edge] 8. In a valve of the type including a housing having a cylindrical bore, two longitudinal spaced flow chambers intersecting the bore, a cylindrical seat land encircling the bore and interposed between the two flow chambers, a plunger reciprocable in the bore and having a peripheral control edge which coacts with the sear land to form a variable area flow path between said chambers, means for shifting the plunger between first and second positions in which the variable area flow path is closed and opened, respectively, and a spring biasing the plunger toward its second position, the improvement which comprises a separate flow path formed in the plunger for providing parallel flow between chambers, the separate path comprising a longitudinal portion and a second portion which extends in a direction normal to the plunger axis from the longitudinal portion through the surface of the plunger at a point spaced from the control edge, the flow area afforded by the separate path being so selected that the axial component of the dynamic reaction force at any position of the plunger is less than the spring bias at the same position.

9. The improvement defined in claim 8 in which the second portion of the separate flow path comprises a circumferential series of radial passages.

10. The improvement defined in claim 9 in which the radial passages are so arranged that they are closed by the cylindrical seat land during a portion of the limited movement of the plunger.

11. The improvement defined in claim 8 in which the longitudinal portion of the separate flow path comprises a conical recess and the second portion comprises a circumferential series of radial passages.

12. The improvement defined in claim 9 in which the diameter of each radial passage is small in relation to its length.

13. In a valve of the type including a housing having a bore for a plunger, two chambers communicating with said bore on opposite sides of a plunger-fitting land, a reciprocable plunger fitting said bore and said land and having a groove serving to bridge said land when the plunger is in its mid position and thus connect the chambers, said groove afiording opposed control edges on the plunger which may selectively overtravel control edges on said land to isolate said chambers when the plunger is displaced from said mid position, and a centering spring biasing the plunger toward its mid position, the improvement which comprises flow passages which lead from said groove through said plunger to the periphery of the plunger, said passages each including a terminal portion which lies in a plane normal to the axis of the plunger and is so located as to be closed by said land only when the plunger is moved from mid position a distance greater than that which causes a control edge on the plunger to overtrovel a control edge on said land, the flow areas afiorded by said flow passages being so selected that the axial component of the dynamic reaction force at any position of the plunger is less than the bias of the centering spring at the same position.

14. In a valve of the type including a housing having a cylindrical bore, two flow chambers communicating with said bore, a seat land encircling sdid bore and separming said chambers, a plunger movable in said bore and having peripheral control edges which coact with said land to define variable area flow paths, means for moving the plunger between a first and second position in each of which the variable flow path is completely closed and at least one position between the first and second positions in which said flow path is open, and a centering spring biasing the plunger toward said one position, the improvement which comprises separate flow 7 8 passages formed in the plunger for afiording flows beforded by said separate flow passages being so selected tween said chambers, said separate flow passages each that the axial component of the dynami reaction force comprising a first portion extending inward beneath one at any position of the plunger is less than the bias of the of said control edges and a second portion extending in centering spring at the same position. a direction normal to the axis of the plunger from said 5 first portion through the surface of the plunger at a N0 references dpoint spaced from the control edge, the flow areas af- 

